The Effect of Uniaxial Mechanical Stretch on Wnt/β-Catenin Pathway in Bone Mesenchymal Stem Cells

Abstract

Wnt/β-catenin signal is required in bone formation and remodling, but little is known about whether Wnt/β-catenin signal could promote osteogenic differentiation of rat bone marrow mesenchymal stem cells (BMSCs) after uniaxial mechanical stretch. In this study, rat BMSCs were identified by flow cytometry and used for mechanical stretch. A custom-made uniaxial dynamic stretch apparatus was applied for rat BMSCs stretch. There were 2 groups in the study: the mechanical stretch group and the nonstretch control group. Cell morphology, alkaline phosphatase (ALP) activity, mRNA levels (Wnt3a, Lrp5, β-catenin, as well as Runx2 were evaluated using quantitative real-time reverse transcription-polymerase chain reaction) and protein levels (β-catenin and Runx2 were examined using western blot) were observed in both groups. The authors finally found that not only the cell proliferation, ALP activity, but also mRNA expression of Wnt3a, Lrp5, β-catenin, and Runx2 in BMSCs were markedly elevated by mechanical stretch than the controls. Protein levels of β-catenin and Runx2 were significantly higher than that of control as well. Activation of mechanical stretch was partially reversed by DKK-1, a classical inhibitor of Wnt/β-catenin signal. These results demonstrate that uniaxial mechanical stretch could stimulate osteogenic differentiation and proliferation of BMSCs by activating the Wnt/β-catenin signaling.

Alterations in β‑catenin/E‑cadherin complex formation during the mechanotransduction of Saos‑2 osteoblastic cells

“…Subsequently, through a series of cytoplasmic protein interactions, β-catenin accumulates in the cytoplasm, translocates to the nucleus and functions with transcription factors, TCF and LEF-1, to activate bone-associated target gene transcription. This pathway is referred to as the classical Wnt/β-catenin pathway, and it has an important role in bone formation ( 24 , 25 ). Loss-of-function mutations in Lrp5 resulted in osteoblast dysfunction and subsequent osteoporosis ( 25 ).…”

“…This pathway is referred to as the classical Wnt/β-catenin pathway, and it has an important role in bone formation ( 24 , 25 ). Loss-of-function mutations in Lrp5 resulted in osteoblast dysfunction and subsequent osteoporosis ( 25 ). Furthermore, Boyden et al ( 26 ) demonstrated that a mutation at position 171 in the Lrp5 protein led to the total loss of dickkopf Wnt signaling pathway inhibitor 1 antagonism in the Wnt signaling pathway in vitro , which resulted in in bone sclerosis.…”

Mechanical forces direct stem cell behaviour in development and regeneration

“…54 Uniaxial stretch of MSCs upregulated the Wnt/β-Catenin pathway, suggesting that mechanical strain promotes proliferation. 98 However, further work is required to determine the magnitude and mode of strain that supports MSC proliferation. Exploiting mechanical cues to maintain and expand stem cell populations in culture is potentially important for scaling up the production of cells for therapeutic applications such as transplantation.…”

Bone remodeling induced by mechanical forces is regulated by miRNAs

“…Indeed, inhibition of endogenous miR-154-5p using an antisense oligonucleotide significantly promoted osteogenic differentiation [ 66 ]. This may partly explain how mechanical stimulation activates the Wnt/β-catenin signaling pathway and promotes bone formation [ 67 ]. Exposure of PDLSCs to stretching force decreased the expression level of activin receptor type IIB (ACVR2B) via a direct interaction of miR-21 with the 3′-untranslated repeat sequence of ACVR2B mRNA [ 68 ].…”